Heading in to his second season in Formula One, Valtteri Bottas is keeping his expectations in check despite the promise shown in pre-season testing.

A strong pre-season, thanks in no small part to the arrival of Mercedes power, has helped propel Williams towards the front, with many suggesting it starts Sunday's Australian Grand Prix as one of the favourites.

"I think it has helped everyone in the team, including me," Bottas said of the upturn in performance. "Now we know that we have a better car than last year we can fight for better positions.

"We need to be careful not to get overexcited and not to stop pushing," he admitted. "We know that it's a long season, especially this year. The key is going to be how much you're going to improve during the season."

It is expected that a number of Renault powered teams, Red Bull and Lotus in particular, will improve as the season wears on, to challenge Williams' current position. It's a battle both Bottas and his team is aware will come, prompting the young Finn to remain cautious.

"Even if you're competitive in the first race doesn't mean that you're going to fight for the title," he warned. "We know and I know it's a long season. There's no need to get over excited."

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Mat Coch